PhSeOTf–Et3N·3HF and PhSeSbF6–Et3N·3HF as new PhSe–F equivalents in the fluoroselenenylation of acetylenes

Abstract

The novel reagents PhSeOTf–Et₃N·3HF and PhSeSbF₆–Et₃N·3HF act as PhSe–F equivalents in the fluoroselenenylation of alkynes. Oct-4-yne, cycloundecyne and cyclododecyne, as well as the unsymmetrical alkynes Ph–CC–Me and Bu–CC–R (R = Me, Et, ⁱPr and ^tBu) give the corresponding (E)-fluoro(phenylseleno)alkenes in preparative yields. The reagent PhSeOTf–Et₃N·3HF gives a similar product composition of regioisomers to Ph₂Se₂–XeF₂ in addition reactions to Bu–CC–R. This is indicative of a similar reaction mechanism of the reagents. Probably a selenirenium ion acts as an intermediate. X-Ray single crystal structure analysis of (E)-1-fluoro-2-phenylselenocycloundecene confirms the trans-addition of [PhSe–F] to cycloundecyne.